Alby Hub subscriptions work based on NWC. The client receives an NWC connection secret with a pay_invoice permission and sends a pay_invoice request to the wallet.
Discussion
Nice, do you know of any services that use this functionality so I can try it out/look at code?
I don't know any public ones, but basically you'd save the NWC connection secret and pull the money according to your subscription terms (e.g. monthly) using the pay_invoice command:
You could look at ZapPlanner: https://github.com/getAlby/ZapPlanner